avcodec/ffwavesynth: Use av_freep() to avoid leaving stale pointers in memory

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/ituh263enc: Check den==0 in ff_h263_aspect_to_info()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avutil/rational: Check that av_reduce() returns values within the requested max

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>